If you start syncing everything we might as well not have gear or stats at all. Old content should be easy. In most rpg games once you beat a part of the game it's laughably easy if you go back... that's a defining charactersitic of advancing your character. Certain mechanics do trump gear though. In BiS gear, with the max echo buff you still have to avoid titan's landslide or get knocked off the platform.

The idea of skill and challange makes me think of Mario brothers or Halo or Darts or Billiards, not final fantasy. In the past I thought of the 'challange' of final fantasy as being more strategic, like Chess... or in the gaming world "Turn Based Strategy." Final Fantasy Tactics, was a "turn based tactics game" which isn't terribly far off from FFXIV where 1 GCD is like a "turn."